Method of enhanced interference measurements for channel state information (CSI) feedback

ABSTRACT

Embodiments of providing enhanced interference measurements for CSI feedback are generally described herein. In some embodiments, CSI-IM resources are used by UE to perform interference measurements. The serving cell determines a hopping pattern for varying a position of the determined CSI-IM resources in subframes transmitted to the served UE. The determined CSI-IM resources and the determined CSI-IM resources hopping pattern are transmitted to the served UE. The serving node transmits a zero-power (ZP) CSI-RS. The serving node receives an interference measurement from the served UE based on CSI-IM and ZP CSI-RS provided to the served LE from the serving cell. Collisions between the CSI-IM of the serving node and CSI-IM of the non-serving nodes are minimized by the determined CSI-IM resources hopping pattern.

This application claims the benefit of priority to U.S. patentapplication Ser. No. 14/027,401, filed on Sep. 16, 2013, which claimsthe benefit of priority to U.S. Provisional Patent Application Ser. No.61/707,784, filed on Sep. 28, 2012, all of which are incorporated hereinby reference in their entireties.

BACKGROUND

Coordinated Multi-Point (CoMP) transmission/reception has been proposedas a promising technology to meet the 3GPP (Third Generation PartnershipProject) LTE-Advanced (LTE-A) requirements by improving performance ofcell-edge UEs in particular. In CoMP operation, multipletransmission/reception points (typically geographically separated, butcould also be co-located) cooperatively transmit to or receive from oneor more users' equipment (UEs) to improve performance, especially theperformance of cell-edge UEs. In the case of downlink CoMP, eachtransmission point, which can have one or more transmit antennas, is aradio unit whose signal covers a geographical area. In general, CoMPtechniques refer to a broad range of coordination mechanisms includinginterference avoidance. CoMP can be used to improve the throughput forcell edge UEs as well as the cell average throughput.

In LTE CRSs may be used by UEs to measure properties of the radiochannel with respect to such CSI parameters as a Channel QualityIndicator, CQI. CSI reference signals (CSI-RS) may be also used byterminals to acquire channel-state information. CSI-RS have asignificantly lower time/frequency density, thus implying less overhead,compared to the CRS. In CoMP systems the channel measurement for CSIfeedback are based on CSI-RS.

For purpose of CSI feedback, interference can be measured on CRS aftersubtracting channel information from received signals or directly on thechannel state information interference measurement resources (CSI-IM)indicated by the network. In CoMP systems the interference measurementsfor CSI are based on CSI-IM due to its flexibility in supportingmeasurement for different interference scenarios. However theinterference measurement using CSI-IM in some cases may be less accuratethan interference measurements cell-specific reference signal (CRS). Theless accurate interference measurements on CSI-IM results from the usageof the resource elements (REs) of zero-power channel state informationreference signal (ZP CSI-RS) which in case of overlap with anotherCSI-IM configured on another cell may not capture interference from someof the transmission points.

In contrast, CRS based measurements in the same cases may includeinterference contribution from the transmitting points even when CRSoverlap. This indicates that for high loading scenario, CRS basedinterference measurements may be more accurate than interferencemeasurements on CSI-IM primary due to smaller number of CSI-IMconfigurations than CRS sequences.

For CSI-IM interference measurements network indicates to a UE whichresource elements (i.e. subcarrier and symbols) the UE is to use toperform interference measurements. The serving cell (node) may nottransmit any data on a given resource elements to remove own-cellinterference, which can be achieved by configuring ZP CSI-RSs on thesame resource elements. The other nodes will transmit data on specifiedresource elements. Thus, the UE measures interference from the othernodes, e.g., coordinating or neighboring cells. A similar CSI-IMmeasurements and configurations may be applied in the neighboring nodes.However, due to the limited number of configurations available,collisions between CSI-IM of different nodes will occur. Thusinterference from some nodes will not be estimated because of thecollisions. This leads to under estimation of interference for CSIfeedback.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless telecommunications network according to anembodiment;

FIG. 2 illustrates a frame structure according to an embodiment;

FIG. 3 illustrates usage of a current CSI-IM resource configuration;

FIG. 4 illustrates usage of CSI-IM resource configuration according toan embodiment;

FIG. 5 illustrates CSI-IM hopping in a time domain according to anembodiment;

FIG. 6 shows an CSI-IM pool according to an embodiment;

FIG. 7 illustrates a simpler case of CSI-IM hopping in a time domainaccording to an embodiment;

FIG. 8 illustrates the use of more than one CSI-IM configurationextension according to an embodiment;

FIG. 9 show a table of the parameters for CSI-RS subframe configurationfor CSI-IM according to an embodiment;

FIG. 10 is a flow chart of a method for providing enhanced interferencemeasurements for CSI feedback according to an embodiment;

FIG. 11 illustrates an extended CSI-IM configuration according to anembodiment;

FIG. 12 illustrates a block diagram of an example machine for providingenhanced interference measurements with CSI feedback according to anembodiment; and

FIG. 13 illustrates a node according to an embodiment.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass available equivalents ofthose claims.

Embodiments provide enhanced interference measurements for CSI feedback.CSI-IM resources are used by UE to perform interference measurements.According to an embodiment, CSI-IM hopping and/or an increase in anumber of CSI-IM resources may be used to provide enhanced interferencemeasurements for CSI feedback.

FIG. 1 illustrates a wireless telecommunications network 100 accordingto an embodiment. The illustrative telecommunications network includeseNBs 110, 120 and 130. A telecommunications network may include manymore eNBs. Each of eNBs 110, 120 and 130 are operable over correspondingcoverage areas or cells 112, 122 and 132. Each base station's coveragearea 112, 122 and 132 may further be divided into three sectors, e.g.,sectors 140, 142, 144, 150, 152, 154, and 160, 162, 164, respectively.In some cases each sector of eNB can be also viewed as a cell. Handsetor other user equipment (UE) 170 is shown in sector A 140. Sector A 140is within coverage area 112 of eNB 110. UE 170 transmits to and receivestransmissions from eNB 110. As UE 170 moves out of Sector A 140 and intoSector B 150, UE 170 may be handed over to eNB 120.

In FIG. 1, UE 170 is shown approaching a cell edge 172 and is servicedby serving eNB 110, UE 170 receives serving signal 180 from serving eNB110. As UE 170 approaches the cell edge 172, the interference 182 fromthe neighboring eNB 120 becomes stronger. UE 170 may be configured byeNB 110 to perform channel and interference measurements using CSI-RSand CSI-IM for CSI feedback.

Performance at the cell-edge 172 is particularly susceptible tointer-cell interference (ICI) 182. Improvements to the performance atthe cell-edge 172 according to an embodiment may be implemented. Asillustrated above, as UE 170 moves away from the serving eNB 110, thedegradation in its SINR can be attributed to two factors. The signalstrength of the received serving signal 180 decreases and ICI 182increases as the UE 170 moves closer to a neighboring eNB 120.

FIG. 2 illustrates a radio frame structure 200 according to anembodiment. In FIG. 2, the radio frame 200 has an overall length of 10ms 214. This is then divided into a total of 20 individual slots 210.Each subframe 212 includes of two slots 210 of length 0.5 ms, and eachslot 210 contains a number of OFDM symbols, N_(symb) 220. Thus, thereare 10 subframes 212 within frame 200. Subframe #18 is shown expandedwith reference to a subcarrier (frequency) axis 216 and an OFDM symbol(time)) axis 218.

A resource element (RE) 230 is the smallest identifiable unit oftransmission and includes a subcarrier 232 for an OFDM symbol period234. Transmissions are scheduled in larger units called resource blocks(RBs) 240 which comprise a number of adjacent subcarriers 232 for aperiod of one 0.5 ms timeslot. Accordingly, the smallest dimensionalunit for assigning resources in the frequency domain is a “resourceblock” (RB) 240, i.e., a group of N_(sc) ^(RB) adjacent subcarriers 232constitute a resource block (RB) 240. Each subframe 212 includes“N_(RB)” resource blocks, i.e., the total number of the subcarrierswithin subframe N_(RB)×N_(sc) ^(RB) 250.

The CSI-IM resource elements may be configured as resource elements ofzero-power (ZP) CSI-RS. ZP CSI-RS may be referred to as muted CSI-RSs ormuted resource elements (REs). A zero-power CSI-RS is a CSI-RS patternwherein the resource elements are not used, i.e., there is notransmitted signal on those resource elements. In some cases zero-powerCSI-RS is a set of REs, where UE may assume no transmission. Therefore,a ZP CSI-RS has the same structure as a non-muted CSI-RS except thatnothing is actually transmitted on the corresponding resource elements.One use of ZP CSI-RS is to be able to create “transmission holes”corresponding to data transmissions in other (neighboring) cells tofacilitate interference measurement using CSI-IM. Another intention ofZP CSI-RS is to be able to create “transmission holes” corresponding toactual CSI-RS transmissions in other (neighboring) cells. This makes itpossible for a terminal to receive CSI-RS of neighboring cells withoutinterference from CSI-RS transmissions in its own cell. Accordingly, ZPCSI-RSs may be used to raise the signal-to-interference-plus-noise ratio(SINR) for CSI-RS in a given cell by configuring ZP CSI-RS ininterfering cells so that the resource elements that otherwise causeinterference are silent.

One or several CSI-IMs may be configured by the network for the purposeof interference measurements (e.g. to have different interferencemeasurements for CSIs corresponding to data blanking or datatransmission from cooperating node(s)).

FIG. 3 illustrates usage of a current CSI-IM resource configuration 300.The illustration in FIG. 3 is a simplified representation. However,those skilled in the art will generalize CSI-IM representation inaccordance to the LTE specification. In FIG. 3, subframes 310 having twoCSI-IMs 320, 322 are shown over time 330. CSI-IM₁ 320 in FIG. 3 isconfigured by two parameters resourceConfig0 340 and subframeConfig0342. The parameter, resourceConfig0 340 defines the positions of theCSI-IM resources for CSI-IM₁ 320 within a subframe. The subframeConfig0342 defines the CSI-IM periodicity and the CSI-IM subframe offset forCSI-IM₁ 320. CSI-IM₂ 322 similarly includes resourceConfig1 350 andsubframeConfig1 352 parameters which may be different thanresourceConfig0 340 and subframeConfig0 342 of CSI-IM₁. Over time, theCSI-IMs are mapped in the subframes in a defined manner. For example, inFIG. 3, each subframe shows CSI-IM₁ at a first position and CSI-IM₂ at asecond position. Thus, the CSI-IM resources 320, 322 have a fixedposition in the subframes 310. In the case of interference measurementsZP CSI-RS resources may be configured on the REs where CSI-IM resources(CSI-IM₁ and CSI-IM₂) are configured for the UE to remove own-cellinterference and to capture interference from neighboring cells.

FIG. 4 is simplified illustration of CSI-IM resource configuration 400according to an embodiment. Enhanced interference measurements areprovided by using CSI-IM hopping and/or by increasing the number ofpossible CSI-IM resources according to an embodiment. In accordance tothe embodiment CSI-IM configuration for enhanced interferencemeasurement may include additional parameters set resourceConfig1 andsubframeConfig1 to increase the number of CSI-IM resources and/orprovide CSI-IM resource hopping in time.

FIG. 4 shows subframes 410 having two CSI-IMs 420, 422 transmitted overtime 430 according to an embodiment. However, those skilled in the artwill recognize extended CSI-IM configuration with additional CSI-IMresources and more complex CSI-IM resource hopping may be implemented.CSI-IM₁ 420 in FIG. 4 includes two parameters {resourceConfig0 440,subframeConfig0 442} and {resourceConfig1 460, subframeConfig1 462}.However, there may be only one resourceConfig that is used withdifferent subframe types, e.g., one resourceConfig and a plurality ofsubframeConfig. Similarly CSI-IM₂ may also include two parameter sets.However the embodiments described herein are not meant to be limited inthis respect. In FIG. 4, CSI-IM₂ 422 is shown in the same position,i.e., position 2, as illustrated above with reference to FIG. 3.However, the second subframe 412 in FIG. 4 shows CSI-IM₁ 420 in thesecond position corresponding to additional parameters resourceConfig1460 and subframeConfig1 462. In the same subframe CSI-IM₂ 422 has hoppedto the first position. As can be seen in the subsequent subframes,CSI-IM₁ 420 and CSI-IM₂ 422 continue to hop to a different position eachsubframe. In some embodiments the CSI-IM configuration can be enhancedby using one additional parameter resourceConfig1 460 or subframeConfig1462.

As shown in FIG. 4, resource elements used by a UE to performinterference measurements will hop in the time domain. If a CSI-IMcollision happens to occur on one subframe, e.g., subframe 420, acollision is unlikely on the next subframe, e.g., subframe 422. Theposition parameter, resourceConfig0 440 defines the positions of theCSI-IM resources for CSI-IM₁ 420. The subframeConfig0 442 defines theCSI-IM periodicity and the CSI-IM subframe offset for CSI-IM₁ 420. InFIG. 4, the resourceConfig0 440 defines a CSI-IM position in thesubframe with periodicity of 10 ms. Thus, subframe 410 repeats againafter 10 ms. The position of CSI-IM₁ in subframe 412 is defined byresourceConfig0 460, which is also have periodicity of 10 ms in FIG. 4.The subframe shift for CSI-IM₁ is defined by subframeConfig0 442 andsubframeConfig1 462. Thus, in FIG. 4, the subframe shift is 5 ms and theCSI-IM₁ resource hop after 5 ms. A similar configuration is shown forCSI-IM₂ which also provides CSI-IM hop after 5 ms.

In another embodiment pseudo-random hopping of CSI-IM may be implementedto avoid or reduce the likelihood of the occurrence of collisions. Ifthe hopping of CSI-IM is enabled, the CSI-IM resources within subframein the cells changes in every time slot or subframe in a pseudo-randomfashion, thus avoiding systematic collisions of the CSI-IM in theneighboring cells.

CSI-IM resource hopping may be limited to the pool of CSI-IM resourceswhich may be subset of the configured resources ZP CSI-RS resources. Thepool CSI-IM resources may be configured by the radio resource control(RRC) protocol message. The particular CSI-IM resource from the CSI-IMpool can be determined in accordance to the pseudo-random sequencegenerated using seed c_(init), where c_(init) may be a function of slotindex, symbol, physical Cell ID and cyclic prefix (CP) type. Thegenerated pseudo-random sequence is then limited to the maximum numberof the available CSI-IM configurations (resources) within the configuredCSI-IM resource pool.

The CSI-IM resource index δ′_(IM) from the CSI-IM resource pool whichmay be used for interference measurement on a given slot or subframe,may be determined according to:δ′_(IM) =P _(CSI-IM){(ƒ_(ih)(n _(s))+δ_(IM))mod N _(CSI-IM)}

where δ_(IM) is the CSI-IM index corresponding to the configured CSI-IMfor the UE by resourceConfig, n_(s) is the slot or subframe number,P_(CSI-IM) is the CSI-IM resource pool, ƒ_(ih) is a random value forselecting a CSI-IM from P_(CSI-IM), and N_(CSI-IM) is a total number ofCSI-IM resources in the configured CSI-IM resource pool.

The pseudo-random sequence hopping function can be defined by

${f_{ih}\left( n_{s} \right)} = \left\{ {{{\begin{matrix}0 \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}}\end{matrix}{if}{\;\mspace{11mu}}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}{if}\mspace{14mu}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}},} \right.$where the pseudo-random sequence c(i) may be initialized with c_(init)at the beginning of each radio frame or set of radio frames. Thefunction ƒ_(ih) (n_(s)) identifies a CSI-IM to randomly select from theCSI-IM resource pool, P_(CSI-IM). According to an embodiment,pseudo-random sequences may be determined from a length-31 Goldsequence. The output sequence c(n) of length M_(PN), where n=0, 1, . . ., M_(PN)−1, is defined byc(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod 2x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n)) mod 2where N_(C)=1600 and the first m-sequence shall be initialized withx₁(0)=1, x₁ (n)=0, n=1, 2, . . . , 30. The initialization of the secondm-sequence is denoted by

$c_{init} = {\sum\limits_{i = 0}^{30}{{x_{2}(i)} \cdot {2^{i}.}}}$

To ensure the planning of CSI-IM resources within coordinated multipointtransmission and reception (CoMP) cluster, the same hooping pattern maybe used by cooperating cells by using the same c_(init) value. Theparameter c_(init) can be independently configured for the UE using RRCsignaling or derived from the physical cell ID, virtual cell ID valuen_(ID) of one of configured CSI-RS resources.

FIG. 5 illustrates CSI-IM hopping in a time domain 500 according to anembodiment. On a given subframe the actual CSI-IM for interferencemeasurements is selected by the UE from a set P_(CSI-IM) 510. e.g., apool of CSI-IM resources which may be subset of configured ZP CSI-RSresources. FIG. 5 shows the example of CSI-IM hopping for the moregeneral case of CoMP system with three base stations (BS), BS₁ 520, BS₂522, BS₃ 524. In subframe i 530, a pool of CSI-IM resources for CSI-IMresource hopping for three base stations (BS), BS₁ 520, BS₂ 522, BS₃524, is shown.

In subframe i 530, PDSCH emulation 540, 544 is provided in resourceelements corresponding to columns 1 and 3 of the second row 550, whereincolumns 1 and 3 correspond to BS₁ 520 and BS₃ 524. No PDSCH transmission542 is performed on the REs of CSI-IM resource as shown in the secondrow 550 of the second column corresponding to BS₂ 522. In subframe i+n532, no PDSCH transmission for BS₂ 522 and PDSH emulation 540, 544 forBS₁ 420 and BS₃ 524 are used in row seven 552. In subframe i+2·n 534,the ZP CSI-RS 542 for BS₂ 522 and PDSH emulation 540, 544 for BS₁ 520and BS₃ 524 are used in row three 554. By randomly hopping of CS-IM 542,CSI-IM collisions between the CoMP cluster of BS₁ 520, BS₂ 522, BS₃ 524and another CoMP cluster are reduced.

FIG. 6 shows a CSI-IM pool 600 according to an embodiment. A pool 610 ofCSI-IM resources for CSI-IM hopping is provided. In FIG. 6, the pool 610includes 10 CSI-IM 620-638 for interference measurement hopping. Toenable CQI calculation for different interference hypothesis, sevenCSI-IM resources are configured, e.g., 620, 622, 626, 634, 636, 638,having cells transmit data, and resources 624, 628, 630, 632 areconfigured not to transmit data. To avoid the potential issues withPDSCH RE mapping, the PDSCH transmission on CSI-IM pool 610 may beavoided by configuring ZP CSI-RS resources on the resource elements ofCSI-IM pool. As PDSCH transmission is not performed on ZP CSI-RS theevolved NodeB (eNB) may need to emulate PDSCH transmission on someresource elements within CSI-IM pool to guarantee interferencemeasurements at the UE according to the interference hypothesis set forthe particular CSI-IM resource. Referring to CSI-IM in the first row,the cell associated with first column and the cell associated with thesecond columns transmit data, but the cell associated with third columnsdoes not transmit data. Thus, the UE measuring interference on the REscorresponding to the first row will capture interference for the cellassociated with columns 1 and the cell associated with columns 2.

FIG. 7 illustrates a simpler case of CSI-IM hopping in a time domain 700according to an embodiment. In FIG. 7, one BS 720 is shown withoutsupport for CoMP according to an embodiment. A CSI-IM 742 is time hoppedfrom row two 750, to row six 752, to row three 754 in subframes i 730,i+n 732 and i+2·n 734, respectively.

FIG. 8 illustrates the use of more than one CSI-IM configuration 800according to an embodiment. In FIG. 8 a subframe 810 is shown with twoCSI-IM resources, CSI-IM₁ 820, CSI-IM₂ 830. CSI-IM₁ 820 includessubframeConfig0 822 and resourceConfig0 824. CSI-IM₂ 830 includessubframeConfig1-N 832 and subframeConfig 1-N 834. Thus, a CSI-IMresource, e.g., CSI-IM₂ 830, may indicate more resource elements forinterference measurements than CSI-IM₁.

FIG. 9 show a table 900 of the parameters for CSI-RS subframeconfiguration which are used for CSI-IM subframe configuration(subframeConfig parameter) according to an embodiment. For subframesconfigured for CSI-RS transmission, the reference signal sequencer_(l,n) _(s) (m) is mapped to complex-valued modulation symbols ak,l(p)used as reference symbols. Thus, the parameter resourceConfig gives theRE pattern of the CSI-RS within the sub-frame or in other words definesthe pattern of CSI-RS used within a subframe. In FIG. 9, the table showsCSI-RS periodicity T_(CSI-RS) 910 and CSI-RS subframe offset Δ_(CSI-RS)920 for a range of CSI-RS subframe configurations 940. For example, theCSI-RS periodicity T_(CSI-RS) 920 is 5 subframes 912 for CSI-RSsubframeConfig 0-4 942 and the CSI-RS subframe offset Δ_(CSI-RS) 920 is0 922. Thus, the CSI-RS periodicity T_(CSI-RS) 920 may range from T=5 to80 subframes. The offset may range from 0 to 79 subframes. Accordingly,a CSI-IM resource configuration may include resourceConfig0,subframeConfig0. The CSI-IM resource configuration may also includeresourceConfig1 and subframeConfig1.

FIG. 10 is a flow chart 1000 of a method for providing enhancedinterference measurements for CSI feedback according to an embodiment.In FIG. 10, CSI-IM resources are determined to perform interferencemeasurements 1010. A hopping pattern is determined for varying aposition of the determined CSI-IM resources in subframes 1020. Thedetermined CSI-IM resources and the determined CSI-IM resources hoppingpattern are provided to other nodes and a UE 1030. A serving node mayconfigure a zero-power (ZP) CSI-RS according to the determined CSI-IMresources and the determined CSI-IM resources hopping pattern 1040. Aninterference measurement is performed by UE based on CSI-IM received bythe UE and the ZP CSI-RS. Channel state information feedback is providedto the serving node based on the interference measurements 1060.Collisions between the CSI-IM of the serving node and CSI-IM of othernodes are minimized by the determined CSI-IM resources hopping pattern1070.

FIG. 11 illustrates an extended CSI-IM configuration 1100 according toan embodiment. In FIG. 11, a frame 1110 is shown including 10 subframes1120. A configured CSI-IM resource within a subset of the subframes 1120may be used to derive the interference measurement. In accordance to theLTE-A specification the CSI-IM is defined by two parameters, i.e.,subframeConfig and resourceConfig that describe the set of downlinksubframes and resource elements respectively, where CSI-IM istransmitted.

The extended CSI-IM configuration 1100, according to an embodiment,includes subframe 0 1130 that includes a parameter subframeConfig0 1132for describing a set of downlink subframes for a first interferencemeasurement. Subframe 4 1140 includes a parameter subframeConfig1 1142for describing a set of downlink subframes for a second interferencemeasurement.

According to 3GPP Release-11, a CSI-IM configuration is a subset ofresource elements configured as zero-power CSI-RS. From a practicalconsideration, support of interference measurements for in systems withdynamic DL to UL configuration using a single CSI process is preferable.However with a single CSI process, one CSI-IM configuration may besupported by the UE. In this case, CSI-IM resource transmissionsresiding on different types of downlink subframes, e.g., flexible 1150and non-flexible, may not be possible. This is due to CSI-IM periodicityof a multiple of 5 ms.

The extended CSI-IM configuration 1100 according to an embodimentprovides an extended CSI-IM configuration that includes parametersubframeConfig1 1142. Independent interference measurements for flexible1150 and non-flexible subframes may thus be achieved by using subframesets.

FIG. 12 illustrates a block diagram of an example machine 1200 forproviding enhanced interference measurements with CSI feedback accordingto an embodiment upon which any one or more of the techniques (e.g.,methodologies) discussed herein may perform. In alternative embodiments,the machine 1200 may operate as a standalone device or may be connected(e.g., networked) to other machines. In a networked deployment, themachine 1200 may operate in the capacity of a server machine and/or aclient machine in server-client network environments. In an example, themachine 1200 may act as a peer machine in peer-to-peer (P2P) (or otherdistributed) network environment. The machine 1200 may be a personalcomputer (PC), a tablet PC, a set-top box (STB), a Personal DigitalAssistant (PDA), a mobile telephone, a web appliance, a network router,switch or bridge, or any machine capable of executing instructions(sequential or otherwise) that specify actions to be taken by thatmachine. Further, while a single machine is illustrated, the term“machine” shall also be taken to include any collection of machines thatindividually or jointly execute a set (or multiple sets) of instructionsto perform any one or more of the methodologies discussed herein, suchas cloud computing, software as a service (SaaS), other computer clusterconfigurations.

Examples, as described herein, may include, or may operate on, logic ora number of components, modules, or mechanisms. Modules are tangibleentities (e.g., hardware) capable of performing specified operations andmay be configured or arranged in a certain manner. In an example,circuits may be arranged (e.g., internally or with respect to externalentities such as other circuits) in a specified manner as a module. Inan example, at least a part of one or more computer systems (e.g., astandalone, client or server computer system) or one or more hardwareprocessors 1202 may be configured by firmware or software (e.g.,instructions, an application portion, or an application) as a modulethat operates to perform specified operations. In an example, thesoftware may reside on at least one machine readable medium. In anexample, the software, when executed by the underlying hardware of themodule, causes the hardware to perform the specified operations.

Accordingly, the term “module” is understood to encompass a tangibleentity, be that an entity that is physically constructed, specificallyconfigured (e.g., hardwired), or temporarily (e.g., transitorily)configured (e.g., programmed) to operate in a specified manner or toperform at least part of any operation described herein. Consideringexamples in which modules are temporarily configured, a module need notbe instantiated at any one moment in time. For example, where themodules comprise a general-purpose hardware processor 1202 configuredusing software; the general-purpose hardware processor may be configuredas respective different modules at different times. Software mayaccordingly configure a hardware processor, for example, to constitute aparticular module at one instance of time and to constitute a differentmodule at a different instance of time. The term “application,” orvariants thereof, is used expansively herein to include routines,program modules, programs, components, and the like, and may beimplemented on various system configurations, including single-processoror multiprocessor systems, microprocessor-based electronics, single-coreor multi-core systems, combinations thereof, and the like. Thus, theterm application may be used to refer to an embodiment of software or tohardware arranged to perform at least part of any operation describedherein.

Machine (e.g., computer system) 1200 may include a hardware processor1202 (e.g., a central processing unit (CPU), a graphics processing unit(GPU), a hardware processor core, or any combination thereof), a mainmemory 1204 and a static memory 1206, at least some of which maycommunicate with others via an interlink (e.g., bus) 1208. The machine1200 may further include a display unit 1210, an alphanumeric inputdevice 1212 (e.g., a keyboard), and a user interface (UI) navigationdevice 1214 (e.g., a mouse). In an example, the display unit 1210, inputdevice 1212 and UI navigation device 1214 may be a touch screen display.The machine 1200 may additionally include a storage device (e.g., driveunit) 1216, a signal generation device 1218 (e.g., a speaker), a networkinterface device 1220, and one or more sensors 1221, such as a globalpositioning system (GPS) sensor, compass, accelerometer, or othersensor. The machine 1200 may include an output controller 1228, such asa serial (e.g., universal serial bus (USB), parallel, or other wired orwireless (e.g., infrared (IR)) connection to communicate or control oneor more peripheral devices (e.g., a printer, card reader, etc.).

The storage device 1216 may include at least one machine readable medium1222 on which is stored one or more sets of data structures orinstructions 1224 (e.g., software) embodying or utilized by any one ormore of the techniques or functions described herein. The instructions1224 may also reside, at least partially, additional machine readablememories such as main memory 1204, static memory 1206, or within thehardware processor 1202 during execution thereof by the machine 1200. Inan example, one or any combination of the hardware processor 1202, themain memory 1204, the static memory 1206, or the storage device 1216 mayconstitute machine readable media.

While the machine readable medium 1222 is illustrated as a singlemedium, the term “machine readable medium” may include a single mediumor multiple media (e.g., a centralized or distributed database, and/orassociated caches and servers) that configured to store the one or moreinstructions 1224.

The term “machine readable medium” may include any medium that iscapable of storing, encoding, or carrying instructions for execution bythe machine 1200 and that cause the machine 1200 to perform any one ormore of the techniques of the present disclosure, or that is capable ofstoring, encoding or carrying data structures used by or associated withsuch instructions. Non-limiting machine readable medium examples mayinclude solid-state memories, and optical and magnetic media. Specificexamples of machine readable media may include: non-volatile memory,such as semiconductor memory devices (e.g., Electrically ProgrammableRead-Only Memory (EPROM), Electrically Erasable Programmable Read-OnlyMemory (EEPROM)) and flash memory devices; magnetic disks, such asinternal hard disks and removable disks; magneto-optical disks; andCD-ROM and DVD-ROM disks.

The instructions 1224 may further be transmitted or received over acommunications network 1226 using a transmission medium via the networkinterface device 1220 utilizing any one of a number of transferprotocols (e.g., frame relay, internet protocol (IP), transmissioncontrol protocol (TCP), user datagram protocol (UDP), hypertext transferprotocol (HTTP), etc.). Example communication networks may include alocal area network (LAN), a wide area network (WAN), a packet datanetwork (e.g., the Internet), mobile telephone networks ((e.g., channelaccess methods including Code Division Multiple Access (CDMA),Time-division multiple access (TDMA), Frequency-division multiple access(FDMA), and Orthogonal Frequency Division Multiple Access (OFDMA) andcellular networks such as Global System for Mobile Communications (GSM),Universal Mobile Telecommunications System (UMTS), CDMA 2000 1×*standards and Long Term Evolution (LTE)), Plain Old Telephone (POTS)networks, and wireless data networks (e.g., Institute of Electrical andElectronics Engineers (IEEE) 802 family of standards including IEEE802.11 standards (WiFi), IEEE 802.16 standards (WiMax®) and others),peer-to-peer (P2P) networks, or other protocols now known or laterdeveloped.

For example, the network interface device 1220 may include one or morephysical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or moreantennas to connect to the communications network 1226. In an example,the network interface device 1220 may include a plurality of antennas towirelessly communicate using at least one of single-inputmultiple-output (SIMO), multiple-input multiple-output (MIMO), ormultiple-input single-output (MISO) techniques. The term “transmissionmedium” shall be taken to include any intangible medium that is capableof storing, encoding or carrying instructions for execution by themachine 1200, and includes digital or analog communications signals orother intangible medium to facilitate communication of such software.

FIG. 13 illustrates a node 1300 according to an embodiment. In FIG. 13,a processor 1310 is coupled to a transceiver 1320 and memory 1330.Communications signals are radiated and intercepted via an antenna 1340.The transceiver 1320 processes signals for transmission or receivedsignals. The memory 1330 may be used to store data including a pool ofZP CSI-RS interference measurement resources 1332.

The processor 1310 determines CSI-IM resources for use by a userequipment (UE) served by the node to perform interference measurementsfor CSI. The processor determines a hopping pattern for varying aposition of the determined CSI-IM resources in subframes transmitted tothe served UE. The determined CSI-IM resources and the determined CSI-IMresources hopping pattern are provided to the transceiver 1320 fortransmission to nodes and to the UE. A zero-power (ZP) CSI-RS accordingto the determined CSI-IM resources and the determined CSI-IM resourceshopping pattern are provided to the transceiver for transmission to theserved UE. A received interference measurement from the served UE basedon CSI-IM received by the served UE and the ZP CSI-RS provided to theserved UE is processed by the processor 1310. Collisions between theCSI-IM transmitted by the transceiver 1320 and CSI-IM of the neighboringnodes are minimized by the determined CSI-IM resources hopping pattern.The processor 1310 is further arranged to generate pseudo-random numbersand to define a position value of the CSI-IM resources to cause theposition of the CSI-IM resources in subframes to vary in the time domainusing the pseudo-random numbers. The processor 1310 also selects asubframe periodicity and an offset for the subframes. The hoppingpattern is defined by at least two CSI-RS parameters resourceConfig andthe periodicity and offset are defined by at least two CSI-RS parametersubframeConfig. The processor 1310 may also determine a hopping patternthat is defined according to

${f_{ih}\left( n_{s} \right)} = \left\{ {{{\begin{matrix}0 \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}}\end{matrix}{if}{\;\mspace{11mu}}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}{if}\mspace{14mu}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from a CSI-IMresource pool, P_(CSI-IM), (n_(s)), where n_(s) is a identifier of aslot or subframe, N_(CSI-IM) is a number of CSI-IM resources in theconfigured CSI-IM resource pool and c(i) is a pseudo-random sequence.

Additional Notes & Examples

Example 1 may include subject matter (such as a method or means forperforming acts) including determining, by a serving cell, CSI-IMresources for use by a served user equipment (UE) to performinterference measurements, transmitting the determined CSI-IM resourcesto the served UE using RRC signaling, transmitting, by the serving cell,a zero-power (ZP) CSI-RS according to the determined CSI-IM resourcesusing RRC signaling to remove serving cell interference and receiving,by the serving cell, CSI feedback corresponding to interferencemeasurements performed by the served UE using CSI-IM received by theserved UE from the serving cell and the ZP CSI-RS transmitted to theserved UE from the serving cell.

Example 2 may optionally include the subject matter of Example 1,further including generating by a serving cell, pseudo-random numbersand defining, by the serving cell, a position value of the CSI-IMresource to cause the position of the CSI-IM resources in subframes tovary in a time domain using the pseudo-random numbers.

Example 3 may optionally include the subject matter of any one or moreof Examples 1-2, further comprising providing, by the serving cell, aplurality of CSI-IM resources in a subframe, wherein the determining, bythe serving cell, the CSI-IM resources to provide in subframes furthercomprises selecting, by the serving cell, a subframe periodicity and anoffset for the subframes.

Example 4 may optionally include the subject matter of any one or moreof Examples 1-3, further comprising determining, by the serving cell, ahopping pattern for varying a position of the determined CSI-IMresources in subframes transmitted to a served UE using at least twoCSI-RS resourceConfig messages, transmitting the determined CSI-IMresources hopping pattern to the served UE using RRC signaling, whereinthe determining the hopping pattern comprises selecting a hoppingpattern to minimize collisions between CSI-IM resources of differentnodes and wherein the selecting a subframe periodicity and an offset forthe subframes further comprises defining the periodicity and offsetusing at least two CSI-RS subframeConfig messages.

Example 5 may optionally include the subject matter of any one or moreof Examples 1-4, wherein the determining, by the serving cell, thehopping pattern further comprises defining a pseudo-random sequencehopping function according to:

${f_{ih}\left( n_{s} \right)} = \left\{ {\begin{matrix}0 & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}} \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}} & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}\end{matrix},} \right.$ƒ_(ih) is a random value for selecting the CSI-IM from a configuredCSI-IM resource pool, PCSI-IM, (ns) is an identifier of a subframe,NCSI-IM is a number of CSI-IM resources in the configured CSI-IMresource pool and c(i) is a pseudo-random sequence generated from alength-31 Gold sequence.

Example 6 may optionally include the subject matter of any one or moreof Examples 1-5, wherein the determining, by the serving cell, CSI-IMresources for use by a user equipment (UE) to perform interferencemeasurements further includes determining a plurality of subframeconfigurations and a resource configuration residing on different typesof subframes, a first subframe configuration and resource configurationresiding on a first type of subframe and a second subframe configurationresiding on a second type of subframe.

Example 7 may optionally include the subject matter of any one or moreof Examples 1-6, wherein the determining, by the serving cell, CSI-IMresources for use by a user equipment (UE) to perform interferencemeasurements further comprising determining a first subframe setcomprising a first subframe configuration and a first resourceconfiguration and determining a second subframe set comprising a secondsubframe configuration, wherein the first subframe set and the secondsubframe set are arranged to provide independent interferencemeasurements for flexible and non-flexible subframes.

Example 8 may include subject matter (such as a method or means forperforming acts) including receiving, at a user equipment (UE), CSI-IMresources from a serving cell for use by a UE to perform interferencemeasurements on nodes including the serving cell, receiving a zero-power(ZP) CSI-RS from the serving cell to remove serving cell interference,making interference measurements based on the received CSI-IM resourcesand the ZP CSI-RS and providing channel state information feedback tothe serving cell based on the interference measurements.

Example 9 may optionally include the subject matter of Example 8,wherein the receiving CSI-IM resources from a serving cell furthercomprises receiving CSI-IM resources that include at least two parametersets comprising {resourceConfig0, subframeConfig0} and{subframeConfig1}.

Example 10 may optionally include the subject matter of any one or moreof Examples 8-9, further including further comprising receiving a CSI-IMresources hopping pattern including receiving at least two CSI-RSresourceConfig message defining the hopping pattern and receiving atleast two subframeConfig message defining subframe periodicity andoffset.

Example 11 may optionally include the subject matter of any one or moreof Examples 8-10, wherein the receiving the CSI-IM resources hoppingpattern further comprises receiving a hopping pattern defined accordingto:

${f_{ih}\left( n_{s} \right)} = \left\{ {\begin{matrix}0 & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}} \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}} & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}\end{matrix},} \right.$ƒ_(ih) is a random value for selecting the CSI-IM from a configuredCSI-IM resource pool, PCSI-IM, (ns) is an identifier of a subframe,NCSI-IM is a number of CSI-IM resources in the configured CSI-IMresource pool and c(i) is a pseudo-random sequence generated from alength-31 Gold sequence.

Example 12 may optionally include the subject matter of any one or moreof Examples 8-11, wherein the receiving, by the UE, CSI-IM resources andthe ZP CSI-RS from the serving node in subframes further comprisesreceiving CSI-IM resources and the ZP CSI-RS according to a subframeperiodicity and an offset for the subframes defined by the serving celland provided in the CSI-IM resources received from the serving cell.

Example 13 may optionally include the subject matter of any one or moreof Examples 8-12, wherein the receiving, at the user equipment (UE),CSI-IM resources from a serving cell for use by a UE to performinterference measurements on nodes including the serving cell furthercomprises receiving a plurality of subframe configurations and aresource configuration residing on different types of subframes, a firstsubframe configuration and a first resource configuration residing on afirst type of subframe and a second subframe configuration residing on asecond type of subframe.

Example 14 may optionally include the subject matter of any one or moreof Examples 8-13, wherein the receiving, at the user equipment (UE),CSI-IM resources from a serving cell for use by a UE to performinterference measurements on nodes including the serving cell furthercomprises receiving a first subframe set comprising a first subframeconfiguration and a first resource configuration and receiving a secondsubframe set comprising a second subframe configuration, wherein thefirst subframe set and the second subframe set are arranged to provideindependent interference measurements for flexible and non-flexiblesubframes.

Example 15 may optionally include the subject matter of any one or moreof Examples 8-14, wherein the making interference measurements based onthe received CSI-IM resources further comprises processing the firstsubframe set and the second subframe set and performing interferencemeasurements based on the processed first subframe set and secondsubframe set.

Example 16 may optionally include the subject matter of any one or moreof Examples 8-15, wherein the receiving, at the user equipment (UE),CSI-IM resources from a serving cell for use by a UE to performinterference measurements on nodes including the serving cell furthercomprises receiving at least two parameter sets, the at least twoparameter sets residing on different types of subframes, wherein a firstsubframe configuration and resource configuration reside on a first typeof subframe and a second subframe configuration and resourceconfiguration reside on a second type of subframe, wherein the makinginterference measurements based on the received CSI-IM resources furthercomprises performing interference measurements based on the processed atleast two parameter sets residing on different types of subframes.

Example 17 may optionally include the subject matter of any one or moreof Examples 8-16, further comprising processing a first of the at leasttwo parameter sets comprising a first subframe configuration andresource configuration and a second of the at least two parameter setscomprising a second subframe configuration and resource configuration,wherein the making interference measurements based on the receivedCSI-IM resources further comprises providing independent interferencemeasurements for flexible and non-flexible subframes based on the firstsubframe set and the second subframe set.

Example 18 includes subject matter (such as a device, apparatus, clientor system) for a serving node, including memory for storing datathereon, a processor, coupled to the memory, for processing signalsassociated with communications including data from the memory, atransceiver, coupled to the processor, arranged to transmit and receivesignals associated with communications and at least one antenna forradiating signals for transmission and intercepts signals for reception,wherein the processor is further arranged to determine CSI-IM resourcesfor use by a served user equipment (UE) served by the serving cell toperform interference measurements, provide the determined CSI-IMresources to the transceiver for transmission to the served UE, provide,to the transceiver for transmission to the served UE, a zero-power (ZP)CSI-RS according to the determined CSI-IM resources to remove servingcell interference and process a received interference measurement fromthe served UE based on CSI-IM received by the served UE and the ZPCSI-RS provided to the served UE from the serving cell.

Example 19 may optionally include the subject matter of Example 16-18,wherein the processor is further arranged to generating pseudo-randomnumbers and to define a position value of the CSI-IM resources to causethe position of the CSI-IM resources in subframes to vary in a timedomain using the pseudo-random numbers.

Example 20 may optionally include the subject matter of any one or moreof Examples 18-19, wherein the processor further selecting a subframeperiodicity and an offset for the subframes, wherein the processor isfurther arranged to determine a hopping pattern for varying a positionof the determined CSI-IM resources in subframes transmitted to a servedUE and to provide the determined CSI-IM resources and the determinedCSI-IM resources hopping pattern to the transceiver for transmission tothe served UE using the selected periodicity and offset, whereincollisions between the CSI-IM transmitted by the transceiver and CSI-IMof neighboring nodes are minimized by the determined hopping pattern.

Example 21 may optionally include the subject matter of any one or moreof Examples 18-20 wherein the processor is further arranged to determinethe hopping pattern according to:

${f_{ih}\left( n_{s} \right)} = \left\{ {\begin{matrix}0 & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}} \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}} & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}\end{matrix},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from aconfigured CSI-IM resource pool, PCSI-IM, (ns) is an identifier of asubframe, NCSI-IM is a number of CSI-IM resources in the configuredCSI-IM resource pool and c(i) is a pseudo-random sequence generated froma length-31 Gold sequence.

Example 22 may optionally include the subject matter of any one or moreof Examples 18-21, wherein the processor is further arranged todetermine CSI-IM resources by determining at least two parameter setscomprising {resourceConfig0, subframeConfig0} and {subframeConfig1}, thetwo parameter sets residing on different types of subframes, a firstsubframe configuration and a first resource configuration residing on afirst type of subframe and a second subframe configuration residing on asecond type of subframe.

Example 23 may optionally include the subject matter of any one or moreof Examples 18-22, wherein the processor is further arranged to provideindependent interference measurements for flexible and non-flexiblesubframes based on the at least two parameter sets residing on differenttypes of subframes.

Example 24 includes subject matter (such as a device, apparatus, clientor system) for a user equipment, including a processor for processingsignals associated with communications, a transceiver, coupled to theprocessor, arranged to transmit and receive signals associated withcommunications and wherein the processor is further arranged to receive,from the transceiver, CSI-IM resources from a serving cell using radioresource control signaling, process the received CSI-IM resources toperform interference measurements on nodes including serving cell,process a zero-power (ZP) CSI-RS received at the transceiver from theserving node to remove serving cell interference, perform interferencemeasurements associated with nodes including serving cell based on theCSI-IM resource received at the transceiver from the serving cell andprovide channel state information feedback to the serving cell based onthe interference measurements.

Example 25 may optionally include the subject matter of Example 24,wherein the processor is further arranged to receive CSI-IM and the ZPCSI-RS from the serving cell in subframes according to a subframeperiodicity and an offset for the subframes defined by the serving celland provided in the CSI-IM resources received from the serving cell.

Example 26 may optionally include the subject matter of any one or moreof Examples 24-25, wherein the processor is further arranged to processa CSI-IM resources hopping pattern received at the transceiver from aserving cell for varying a position of the CSI-IM resources in subframesand to receive CSI-IM and the ZP CSI-RS from the serving cell inpositions in subframes according to the received CSI-IM resourceshopping pattern.

Example 27 may optionally include the subject matter of any one or moreof Examples 24-26, wherein the hopping pattern is defined according to:

${f_{ih}\left( n_{s} \right)} = \left\{ {\begin{matrix}0 & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}} \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}} & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}\end{matrix},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from aconfigured CSI-IM resource pool, PCSI-IM, (ns) is an identifier of asubframe, NCSI-IM is a number of CSI-LM resources in the configuredCSI-IM resource pool and c(i) is a pseudo-random sequence generated froma length-31 Gold sequence.

Example 28 may optionally include the subject matter of any one or moreof Examples 24-27, wherein the receiving CSI-IM resources from a servingcell further comprises receiving CSI-IM resources that include at leasttwo parameter sets comprising {resourceConfig0, subframeConfig0} and{subframeConfig1} and wherein the processor is further arranged toprocess the at least two parameter sets, the processor further arrangedto perform interference measurements associated with the nodes includingserving cell based on the processed at least two parameter sets.

Example 29 may optionally include the subject matter of any one or moreof Examples 24-28, wherein the at least two parameter sets reside ondifferent types of subframes, a first subframe configuration andresource configuration residing on a first type of subframe and a secondsubframe configuration residing on a second type of subframe, theprocessor further arranged to perform interference measurements based onthe processed at least two parameter sets residing on different types ofsubframes.

Example 30 may optionally include the subject matter of any one or moreof Examples 24-29, wherein the at least two parameter sets are arrangedto provide independent interference measurements for flexible andnon-flexible subframes.

Example 31 may include subject matter (such as means for performing actsor machine readable medium including instructions that, when executed bythe machine, cause the machine to perform acts) including determining,by a serving cell, CSI-IM resources for use by a served user equipment(UE) to perform interference measurements, transmitting the determinedCSI-IM resources to the served UE using RRC signaling, transmitting, bythe serving cell, a zero-power (ZP) CSI-RS according to the determinedCSI-IM resources using RRC signaling to remove serving cell interferenceand receiving, by the serving cell, CSI feedback corresponding tointerference measurements performed by the served UE using CSI-IMreceived by the served UE from the serving cell and the ZP CSI-RStransmitted to the served UE from the serving cell.

Example 32 may optionally include the subject matter of Example 31,further including generating by a serving cell, pseudo-random numbersand defining, by the serving cell, a position value of the CSI-IMresource to cause the position of the CSI-IM resources in subframes tovary in a time domain using the pseudo-random numbers.

Example 33 may optionally include the subject matter of any one or moreof Examples 31-32, further comprising providing, by the serving cell, aplurality of CSI-IM resources in a subframe, wherein the determining, bythe serving cell, the CSI-IM resources to provide in subframes furthercomprises selecting, by the serving cell, a subframe periodicity and anoffset for the subframes.

Example 34 may optionally include the subject matter of any one or moreof Examples 31-33, further comprising determining, by the serving cell,a hopping pattern for varying a position of the determined CSI-IMresources in subframes transmitted to a served UE using at least twoCSI-RS resourceConfig messages, transmitting the determined CSI-IMresources hopping pattern to the served UE using RRC signaling, whereinthe determining the hopping pattern comprises selecting a hoppingpattern to minimize collisions between CSI-IM resources of differentnodes and wherein the selecting a subframe periodicity and an offset forthe subframes further comprises defining the periodicity and offsetusing at least two CSI-RS subframeConfig messages.

Example 35 may optionally include the subject matter of any one or moreof Examples 31-34, wherein the determining, by the serving cell, thehopping pattern further comprises defining a pseudo-random sequencehopping function according to:

${f_{ih}\left( n_{s} \right)} = \left\{ {\begin{matrix}0 & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}} \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}} & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}\end{matrix},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from aconfigured CSI-IM resource pool, PCSI-IM, (ns) is an identifier of asubframe, NCSI-IM is a number of CSI-IM resources in the configuredCSI-IM resource pool and c(i) is a pseudo-random sequence generated froma length-31 Gold sequence.

Example 36 may optionally include the subject matter of any one or moreof Examples 31-35, wherein the determining, by the serving cell, CSI-IMresources for use by a user equipment (UE) to perform interferencemeasurements further includes determining a plurality of subframeconfigurations and a resource configuration residing on different typesof subframes, a first subframe configuration and resource configurationresiding on a first type of subframe and a second subframe configurationresiding on a second type of subframe.

Example 37 may optionally include the subject matter of any one or moreof Examples 31-36, wherein the determining, by the serving cell, CSI-IMresources for use by a user equipment (UE) to perform interferencemeasurements further comprising determining a first subframe setcomprising a first subframe configuration and a first resourceconfiguration and determining a second subframe set comprising a secondsubframe configuration, wherein the first subframe set and the secondsubframe set are arranged to provide independent interferencemeasurements for flexible and non-flexible subframes.

Example 38 may include subject matter (such as means for performing actsor machine readable medium including instructions that, when executed bythe machine, cause the machine to perform acts) including receiving, ata user equipment (UE), CSI-IM resources from a serving cell for use by aUE to perform interference measurements on nodes including the servingcell, receiving a zero-power (ZP) CSI-RS from the serving cell to removeserving cell interference, making interference measurements based on thereceived CSI-IM resources and the ZP CSI-RS and providing channel stateinformation feedback to the serving cell based on the interferencemeasurements.

Example 39 may optionally include the subject matter of Example 38,wherein the receiving CSI-IM resources from a serving cell furthercomprises receiving CSI-IM resources that include at least two parametersets comprising {resourceConfig0, subframeConfig0} and{subframeConfig1}.

Example 40 may optionally include the subject matter of any one or moreof Examples 38-39, further comprising receiving a CSI-IM resourceshopping pattern including receiving at least two CSI-RS resourceConfigmessage defining the hopping pattern and receiving at least twosubframeConfig message defining subframe periodicity and offset.

Example 41 may optionally include the subject matter of any one or moreof Examples 38-40, wherein the receiving the CSI-IM resources hoppingpattern further comprises receiving a hopping pattern defined accordingto:

${f_{ih}\left( n_{s} \right)} = \left\{ {\begin{matrix}0 & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}} \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}} & {{if}\mspace{14mu}{CSI}\text{-}{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}\end{matrix},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from aconfigured CSI-IM resource pool, PCSI-IM, (ns) is an identifier of asubframe, NCSI-IM is a number of CSI-IM resources in the configuredCSI-IM resource pool and c(i) is a pseudo-random sequence generated froma length-31 Gold sequence.

Example 42 may optionally include the subject matter of any one or moreof Examples 38-41, wherein the receiving, by the UE, CSI-IM resourcesand the ZP CSI-RS from the serving node in subframes further comprisesreceiving CSI-IM resources and the ZP CSI-RS according to a subframeperiodicity and an offset for the subframes defined by the serving celland provided in the CSI-IM resources received from the serving cell.

Example 43 may optionally include the subject matter of any one or moreof Examples 38-42, wherein the receiving, at the user equipment (UE),CSI-IM resources from a serving cell for use by a UE to performinterference measurements on nodes including the serving cell furthercomprises receiving a plurality of subframe configurations and aresource configuration residing on different types of subframes, a firstsubframe configuration and a first resource configuration residing on afirst type of subframe and a second subframe configuration residing on asecond type of subframe.

Example 44 may optionally include the subject matter of any one or moreof Examples 38-43, wherein the receiving, at the user equipment (UE),CSI-IM resources from a serving cell for use by a UE to performinterference measurements on nodes including the serving cell furthercomprises receiving a first subframe set comprising a first subframeconfiguration and a first resource configuration and receiving a secondsubframe set comprising a second subframe configuration, wherein thefirst subframe set and the second subframe set are arranged to provideindependent interference measurements for flexible and non-flexiblesubframes.

Example 45 may optionally include the subject matter of any one or moreof Examples 38-44, wherein the making interference measurements based onthe received CSI-IM resources further comprises processing the firstsubframe set and the second subframe set and performing interferencemeasurements based on the processed first subframe set and secondsubframe set.

Example 46 may optionally include the subject matter of any one or moreof Examples 38-45, wherein the receiving, at the user equipment (UE),CSI-IM resources from a serving cell for use by a UE to performinterference measurements on nodes including the serving cell furthercomprises receiving at least two parameter sets, the at least twoparameter sets residing on different types of subframes, wherein a firstsubframe configuration and resource configuration reside on a first typeof subframe and a second subframe configuration and resourceconfiguration reside on a second type of subframe, wherein the makinginterference measurements based on the received CSI-IM resources furthercomprises performing interference measurements based on the processed atleast two parameter sets residing on different types of subframes.

Example 47 may optionally include the subject matter of any one or moreof Examples 38-46, further comprising processing a first of the at leasttwo parameter sets comprising a first subframe configuration andresource configuration and a second of the at least two parameter setscomprising a second subframe configuration and resource configuration,wherein the making interference measurements based on the receivedCSI-IM resources further comprises providing independent interferencemeasurements for flexible and non-flexible subframes based on the firstsubframe set and the second subframe set.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments that may bepracticed. These embodiments are also referred to herein as “examples.”Such examples may include elements in addition to those shown ordescribed. However, also contemplated are examples that include theelements shown or described. Moreover, also contemplate are examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

Publications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this document and those documents so incorporated byreference, the usage in the incorporated reference(s) are supplementaryto that of this document; for irreconcilable inconsistencies, the usagein this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to suggest a numerical order for their objects.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with others. Otherembodiments may be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is to allow thereader to quickly ascertain the nature of the technical disclosure, forexample, to comply with 37 C.F.R. §1.72(b) in the United States ofAmerica. It is submitted with the understanding that it will not be usedto interpret or limit the scope or meaning of the claims. Also, in theabove Detailed Description, various features may be grouped together tostreamline the disclosure. However, the claims may not set forthfeatures disclosed herein because embodiments may include a subset ofsaid features. Further, embodiments may include fewer features thanthose disclosed in a particular example. Thus, the following claims arehereby incorporated into the Detailed Description, with a claim standingon its own as a separate embodiment. The scope of the embodimentsdisclosed herein is to be determined with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

What is claimed is:
 1. A method for providing enhanced InterferenceMeasurements (IM) for Channel State Information (CSI) feedbackcomprising: generating a pseudo-random sequence; determining ChannelState Information-Interference Measurement (CSI-IM) resources for aserved User Equipment (UE) to perform interference measurements bydefining a position value of the CSI-IM resources to cause the positionof the CSI-IM resources in subframes to vary in a time domain accordingto the pseudo-random sequence; transmitting the determined CSI-IMresources to the served UE; transmitting a Zero Power (ZP) CSI-RSaccording to the determined CSI-IM resources to the served UE; receivingCSI feedback corresponding to the interference measurements performed bythe served UE using the CSI-IM transmitted to the served UE and the ZPCSI-RS transmitted to the served UE; providing a plurality of CSI-IMresources in a subframe; wherein the determining the CSI-IM resources toprovide in subframes further comprises selecting a subframe periodicityand an offset for the subframes; determining a hopping pattern forvarying a position of the determined CSI-IM resources in subframestransmitted to the served UE using at least two CSI-RS resourceConfigmessages; transmitting the determined CSI-IM resources hopping patternto the served UE; wherein the determining the hopping pattern comprisesselecting a hopping pattern to minimize collisions between CSI-IMresources of different serving cells; and wherein the selecting asubframe periodicity and an offset for the subframes further comprisesdefining the periodicity and offset using at least two CSI-RSsubframeConfig messages, wherein the determining the hopping patternfurther comprises: defining a pseudo-random sequence hopping functionaccording to ${f_{ih}\left( n_{s} \right)} = \left\{ {{{\begin{matrix}0 \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}}\end{matrix}{if}{\;\mspace{11mu}}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}{if}\mspace{14mu}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from aconfigured CSI-IM resource pool, P_(CSI-IM), (n_(s)) is an identifier ofa subframe, N_(CSI-IM) is a number of CSI-IM resources in the configuredCSI-IM resource pool and c(i) is a pseudo-random sequence generated froma length-31 Gold sequence.
 2. The method of claim 1, wherein thedetermining CSI-IM resources for the served user equipment (UE) toperform interference measurements further comprises: determining aplurality of subframe configurations and a resource configurationresiding on different types of subframes, a first subframe configurationand the resource configuration residing on a first type of subframe anda second subframe configuration residing on a second type of subframe.3. The method of claim 1, wherein the determining CSI-IM resources forthe served user equipment (UE) to perform the interference measurementsfurther comprising: determining a first subframe set comprising a firstsubframe configuration and a first resource configuration anddetermining a second subframe set comprising a second subframeconfiguration; and wherein the first subframe set and the secondsubframe set are arranged to provide independent interferencemeasurements for flexible and non-flexible subframes.
 4. A method forproviding enhanced Interference Measurements (IM) for Channel StateInformation (CSI) feedback, comprising: receiving, at a User Equipment(UE), Channel State Information-Interference Measurement (CSI-IM)resources from a serving cell for the UE to perform interferencemeasurements on serving cells including the serving cell; receiving aZero Power (ZP) CSI-RS according to the CSI-IM resources from theserving cell; receiving a CSI-IM resources hopping pattern that causesthe position of the CSI-IM resources in subframes to vary in a timedomain according to a pseudo-random sequence, wherein the receivingincludes receiving at least two CSI-RS resourceConfig messages definingthe CSI-IM resources hopping pattern, and receiving at least twosubframeConfig messages defining subframe periodicity and offset of theCSI-IM resources hopping pattern; performing the interferencemeasurements based on the CSI-IM resources and the ZP CSI-RS; andtransmitting Channel State Information (CSI) feedback to the servingcell based on the interference measurements, wherein the receiving theCSI-IM resources hopping pattern further comprises receiving a hoppingpattern defined according to:${f_{ih}\left( n_{s} \right)} = \left\{ {{{\begin{matrix}0 \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}}\end{matrix}{if}{\;\mspace{11mu}}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}{if}\mspace{14mu}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from aconfigured CSI-IM resource pool, P_(CSI-IM), (n_(s)) is an identifier ofa subframe, N_(CSI-IM) is a number of CSI-IM resources in the configuredCSI-IM resource pool and c(i) is a pseudo-random sequence generated froma length-31 Gold sequence.
 5. The method of claim 4, wherein thereceiving CSI-IM resources from a serving cell further comprisesreceiving CSI-IM resources that include at least two parameter setscomprising {resourceConfig0, subframeConfig0} and {subframeConfig1}. 6.The method of claim 4, wherein the receiving the CSI-IM resources andthe ZP CSI-RS from the serving cell in subframes further comprisesreceiving CSI-IM resources and the ZP CSI-RS according to a subframeperiodicity and an offset for the subframes defined by the serving celland provided in the CSI-IM resources received from the serving cell. 7.The method of claim 4, wherein the receiving, at the UE CSI-IM resourcesfrom a serving cell for the UE to perform interference measurements onserving cells including the serving cell further comprises receiving aplurality of subframe configurations and a resource configurationresiding on different types of subframes, a first subframe configurationand the resource configuration residing on a first type of subframe anda second subframe configuration residing on a second type of subframe.8. The method of claim 4, wherein the receiving, at the UE, CSI-IMresources from a serving cell for the UE to perform interferencemeasurements on serving cells including the serving cell furthercomprises receiving a first subframe set comprising a first subframeconfiguration and a first resource configuration and receiving a secondsubframe set comprising a second subframe configuration, wherein thefirst subframe set and the second subframe set are arranged to provideindependent interference measurements for flexible and non-flexiblesubframes.
 9. The method of claim 8, wherein the performing interferencemeasurements based on the CSI-IM resources further comprises processingthe first subframe set and the second subframe set and performinginterference measurements based on the processed first subframe set andsecond subframe set.
 10. The method of claim 4, wherein the receiving,at the UE, CSI-IM resources from a serving cell for the UE to performinterference measurements on serving cells including the serving cellfurther comprises receiving at least two parameter sets, the at leasttwo parameter sets residing on different types of subframes, wherein afirst subframe configuration and resource configuration reside on afirst type of subframe and a second subframe configuration and resourceconfiguration reside on a second type of subframe, wherein theperforming interference measurements based on the CSI-IM resourcesfurther comprises performing interference measurements based on the atleast two parameter sets residing on different types of subframes. 11.The method of claim 4, further comprising processing a first of at leasttwo parameter sets comprising a first subframe configuration andresource configuration and a second of the at least two parameter setscomprising a second subframe configuration and resource configuration,wherein the performing interference measurements based on the CSI-IMresources further comprises providing independent interferencemeasurements for flexible and non-flexible subframes based on the firstsubframe set and the second subframe set.
 12. A circuit for a servingcell comprising: a processor configured to process signals associatedwith communications; a transceiver configured to transmit and receivesignals associated with the communications; wherein the processor isconfigured to: generating a pseudo-random sequence; determine ChannelState Information-Interference Measurement (CSI-IM) resources for aserved User Equipment (UE) served by the serving cell to performinterference measurements by defining a position value of the CSI-IMresources to cause the position of the CSI-IM resources in subframes tovary in a time domain according to the pseudo-random sequence; providethe determined CSI-IM resources to the transceiver for transmission tothe served UE; provide a Zero Power (ZP) CSI-RS according to thedetermined CSI-IM resources to the transceiver for transmission to theserved UE; and process a received interference measurement from theserved UE based on the CSI-IM provided to the served UE from the servingcell and the ZP CSI-RS provided to the served UE from the serving cell,wherein the processor is further configured to select a subframeperiodicity and an offset for the subframes, wherein the processor isfurther configured to determine a hopping pattern for varying a positionof the determined CSI-IM resources in subframes transmitted to a servedUE and to provide the determined CSI-IM resources and the determinedCSI-IM resources hopping pattern to the transceiver for transmission tothe served UE using the selected periodicity and offset, whereincollisions between the CSI-IM transmitted by the transceiver and CSI-IMof neighboring cells are minimized by the determined hopping pattern,wherein the processor is further configured to determine the hoppingpattern according to:${f_{ih}\left( n_{s} \right)} = \left\{ {{{\begin{matrix}0 \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}}\end{matrix}{if}{\;\mspace{11mu}}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}{if}\mspace{14mu}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from aconfigured CSI-IM resource pool, P_(CSI-IM), (n_(s)) is an identifier ofa subframe, N_(CSI-IM) is a number of CSI-IM resources in the configuredCSI-IM resource pool and c(i) is a pseudo-random sequence generated froma length-31 Gold sequence.
 13. The circuit of claim 12, wherein theprocessor is further configured to determine CSI-IM resources bydetermining at least two parameter sets comprising {resourceConfig0,subframeConfig0} and {subframeConfig1}, the two parameter sets residingon different types of subframes, a first subframe configuration and afirst resource configuration residing on a first type of subframe and asecond subframe configuration residing on a second type of subframe. 14.The circuit of claim 13, wherein the processor is further configured toprovide independent interference measurements for flexible andnon-flexible subframes based on the at least two parameter sets residingon different types of subframes.
 15. A User Equipment (UE) comprising: aprocessor configured to process signals associated with communications;a transceiver configured to transmit and receive signals associated withthe communications; wherein the processor is further configured to:receive Channel State Information-Interference Measurement (CSI-IM)resources from a serving cell from the transceiver; process the receivedCSI-IM resources to perform interference measurements on cells includingthe serving cell; process a Zero Power (ZP) CSI-RS according to theCSI-IM resources received at the transceiver from the serving cell;receiving a CSI-IM resources hopping pattern including receiving atleast two CSI-RS resourceConfig messages defining the hopping pattern,and receiving at least two subframeConfig messages defining subframeperiodicity and offset, wherein the hopping pattern is defined accordingto: ${f_{ih}\left( n_{s} \right)} = \left\{ {{{\begin{matrix}0 \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\left\lfloor {n_{s}/2} \right\rfloor} + i} \right)} \cdot 2^{i}}} \right){mod}\mspace{14mu} N_{{CSI} - {IM}}}\end{matrix}{if}{\;\mspace{11mu}}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}{if}\mspace{14mu}{CSI}} - {{IM}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}},} \right.$where ƒ_(ih) is a random value for selecting the CSI-IM from aconfigured CSI-IM resource pool, P_(CSI-IM), (n_(s)) is an identifier ofa subframe, N_(CSI-IM) is a number of CSI-IM resources in the configuredCSI-IM resource pool and c(i) is a pseudo-random sequence generated froma length-31 Gold sequence; perform the interference measurementsassociated with the cells including the serving cell based on the CSI-IMresources and ZP CSI-RS received at the transceiver from the servingcell; and provide CSI feedback to the serving cell based on theinterference measurements.
 16. The UE of claim 15, wherein the processoris further configured to receive CSI-IM and the ZP CSI-RS from theserving cell in subframes according to a subframe periodicity and anoffset for the subframes defined by the serving cell and provided in theCSI-IM resources received from the serving cell.
 17. The UE of claim 15,wherein the receiving CSI-IM resources from a serving cell furthercomprises receiving CSI-IM resources that include at least two parametersets comprising {resourceConfig0, subframeConfig0} and {subframeConfig1}and wherein the processor is further configured to process the at leasttwo parameter sets, the processor further configured to performinterference measurements associated with cells including the servingcell based on the processed at least two parameter sets.
 18. The UE ofclaim 17, wherein the at least two parameter sets reside on differenttypes of subframes, a first subframe configuration and resourceconfiguration residing on a first type of subframe and a second subframeconfiguration residing on a second type of subframe, the processorfurther configured to perform interference measurements based on theprocessed at least two parameter sets residing on different types ofsubframes.
 19. The UE of claim 17, wherein the at least two parametersets are configured to provide independent interference measurements forflexible and non-flexible subframes.